During her college days, Dr. Jane Smith obtained 5000 lb of fish liver to extract pure omega-3 fatty acid, an essential nutrient. Dr. Smith burned a 4.00 mg purified omega-3 fatty acid in oxygen. Later, she determined that it had produced 11.73 mg of CO2 and 4.80 mg of H2O. Derive the empirical formula of omega-3 fatty acid.